Pane having an electrical connection element

ABSTRACT

A pane having an electrical connection element, the pane having: a substrate; an electrically conductive structure in a region of the substrate; and a connection element in a region of the electrically conductive structure, the connection element containing at least a chromium-containing steel. The connection element has a region which is crimped about a connecting cable and a soldering region connected to the electrically conductive structure by means of a lead-free solder.

The invention relates to a pane with an electrical connection element,an economical and environmentally friendly method for its production,and its use.

The invention relates in particular to a pane with an electricalconnection element for motor vehicles with electrically conductivestructures such as, for instance, heating conductors or antennaconductors. The electrically conductive structures are customarilyconnected to the onboard electrical system via soldered-on electricalconnection elements. Due to different coefficients of thermal expansionof the materials used, mechanical stresses occur during production andoperation that strain the panes and can cause breakage of the pane.

Lead-containing solders have high ductility that can compensate themechanical stresses occurring between an electrical connection elementand the pane by plastic deformation. However, because of the End of LifeVehicles Directive 2000/53/EC, lead-containing solders have to bereplaced by lead-free solders within the EC. The directive is referredto, in summary, by the acronym ELV (End of Life Vehicles). Its objectiveis to ban extremely problematic components from products resulting fromthe massive increase in disposable electronics. The substances affectedare lead, mercury, and cadmium. This relates, among other things, to theimplementation of lead-free soldering materials in electricalapplications on glass and the introduction of corresponding replacementproducts.

A number of electrical connection elements for leadfree soldering toelectrically conductive structures have been proposed. Reference ismade, by way of example, to the documents US 20070224842 A1, EP 1942703A2, WO 2007110610 A1, EP 1488972 A1, and EP 2365730 A1. The shape of theconnection element, on the one hand, and the material of the connectionelement, on the other, assume critical significance with regard to theavoidance of thermal stresses.

The object of the present invention is to provide a pane with anelectrical connection element that is particularly suited for solderingusing leadfree solder materials, wherein critical mechanical stresses inthe pane are avoided. Moreover, an economical and environmentallyfriendly method for their production is to be provided.

The object of the present invention is accomplished according to theinvention by a pane with at least one electrical connection elementaccording to the independent claim 1. Preferred embodiments emerge fromthe subclaims.

The pane according to the invention with at least one electricalconnection element comprises at least the following characteristics:

-   -   a substrate,    -   on a region of the substrate, an electrically conductive        structure,    -   on a region of the electrically conductive structure, a        connection element that includes at least a chromium-containing        steel,        wherein the connection element has a region crimped around a        connection cable and a solder region and wherein the solder        region is connected to the electrically conductive structure via        a leadfree solder material.

According to the invention, the electrical connection element isconnected to the connection cable by crimping. The crimp connection issimple, economical, and quick to produce and can be readily automated.Costly additional process steps, for example, soldering or welding theconnection element to the connection cable can be avoided. At the sametime, a very stable connection between the connection element and theconnection cable is provided. The connection element according to theinvention with the crimped region (the so-called crimp, i.e., the regiondeformed by the crimping procedure) can be produced simply andeconomically and enables space-saving, flexibly usable, and durablystable electrical contacting of the electrically conductive structure.

Chromium-containing, in particular so-called “stainless steel” or“corrosion resistant steel” steel is available economically. Connectionelements made of chromium-containing steel also have high rigidity incomparison to many conventional connection elements, made, for example,of copper, which results in an advantageous stability of the crimpedconnection. Chromium-containing steel has good cold formability, becauseof which it is particularly suited for production of crimp connections.In addition, compared to many conventional connection elements, forexample, those made of titanium, chromium-containing steel has improvedsolderability, due to higher thermal conductivity.

The connection cable is provided to electrically connect theelectrically conductive structure to an external functional element, forexample, a power supply or a receiver. For this, the connection cable isguided away from the pane starting from the connection elementpreferably beyond the side edges of the pane. The connection cable can,in principle, be any connection cable that is known to the personskilled in the art for the electrical contacting of an electricallyconductive structure and is suitable for being connected by crimping tothe connection element (also called “crimp contact”). The connectioncable can include, in addition to an electrically conductive core (innerconductor), an insulating, preferably polymer sheathing, with theinsulating sheathing preferably removed in the end region of theconnection cable to enable an electrically conductive connection betweenthe connection element and the inner conductor.

The electrically conductive core of the connection cable can, forexample, include copper, aluminum, and/or silver or alloys or mixturesthereof. The electrically conductive core can, for example, beimplemented as a stranded wire conductor or as a solid wire conductor.The cross-section of the electrically conductive core of the connectioncable depends on the current-carrying capacity required for theapplication of the pane according to the invention and can be selectedappropriately by the person skilled in the art. The cross-section is,for example, from 0.3 mm² to 6 mm².

The connection element, which includes, according to the invention, atleast a chromium-containing steel and is preferably made from thechromium-containing steel, is preferably crimped in the end region ofthe connection cable around the electrically conductiven core of theconnection cable such that a durably stable electrically conductiveconnection is developed between the connection element and theconnection cable. The crimping is done with a suitable crimping tool,known per se to the person skilled in the art, for example, crimpingpliers or a crimping press. Customarily, the crimping tool comprises twoactive points, for example, the jaws of crimping pliers, which areguided against each other, by which means mechanical pressure is exertedon the connection element. The connection element is thus plasticallydeformed and squeezed around the connection element.

In a preferred embodiment of the electrical connection element accordingto the invention, the solder region is disposed on the side of thecrimped region which faces the extension direction of the connectioncable to the external function element. The angle between the solderregion and the crimped region is preferably from 120° to 180°,particularly preferably from 150° to 170°. By this means, a particularlyspace-saving and stable electrical contacting of the electricallyconductive structure can be obtained.

The surface of the solder region facing the substrate forms the contactsurface between the connection element and the electrically conductivestructure and is connected to the electrically conductive structure viathe solder material. Here, this means a direct, mechanical connectionbetween the solder region and the electrically conductive structure viathe solder material. This means that the solder material is disposedbetween the solder region and the electrically conductive structure andthus fixes the solder region durably stably on the electricallyconductive structure.

In the solder region and in the crimped region, the connection elementpreferably has the same material thickness. This is particularlyadvantageous with regard to simple production of the connection element,since the connection element can be punched from a single sheet ofmetal. The material thickness of the connection element is preferablyfrom 0.1 mm to 2 mm, particularly preferably from 0.2 mm to 1 mm, veryparticularly preferably from 0.3 mm to 0.5 mm. In this range for thematerial thickness, the connection element has, on the one hand, thecold formability necessary for the crimping. On the other hand, in thisrange for the material thickness, an advantageous stability of thecrimped connection and an advantageous electrical connection between theelectrically conductive structure and the connection cable are obtained.

The length and the width of the solder region are preferably from 1 mmto 10 mm, particularly preferably from 2 mm to 8 mm, and veryparticularly preferably from 2.5 mm to 5 mm. This is particularlyadvantageous in view of a small space requirement of the connectionelement and effective electrical contacting of the electricallyconductive structure.

In a preferred embodiment, the solder region is implemented flat, whichyields a flat contact surface. However, the solder region can also haveregions introduced by reshaping, such as stamping or deep drawing, forexample, solder depots, spacers, or contact bumps. Apart from thereshaped regions, the contact surface is preferably flat.

The shape of the solder region and of the contact surface can beselected according to the requirements in the individual case and can,for example, be polygonal, rectangular, rectangular with roundedcorners, oval, elliptical, or circular.

The length of the crimped region can be appropriately selected by theperson skilled in the art taking into account the diameter of theconnection cable as well as applicable standards and is, for example,from 2 mm to 8 mm or from 4 mm to 5 mm, in particular 4.5 mm. This isparticularly advantageous in view of a small space requirement of theconnection element and a stable connection between the connectionelement and the connection cable. Preferably, the crimp is implementedas an open crimp. Since, in this case, the connection cable does nothave to be inserted into an all-around closed wire-end ferrule (closedcrimp), such a crimp connection is easier to produce and can be readilyautomated and is, consequently, particularly suited for mass production.The shape of the crimp can be freely selected, for example, as a B-crimpor an O-crimp.

The solder region can be connected directly to the crimped region of theconnection element. However, a transition region, for example, with alength of 1 mm to 5 mm can be disposed between the solder region and thecrimped region. By means of a transition region, the flexibility in thedesign of the connection element is increased.

In addition to the crimped region, one or a plurality of other regionscan be connected to the solder region. For example, another region canbe disposed on the side edge of the solder region opposite the crimpedregion. Such another region can, for example, be provided to connect theconnection element to a mounting bracket. For example, by means of ashared mounting bracket, a plurality of connection elements according tothe invention can be soldered to the electrically conductive structurein a defined relative arrangement.

In an advantageous embodiment, the pane has from two to six electricalconnection elements according to the invention. By means of multipleconnection elements, an electrically conductive structure implemented asa heating conductor can, for example, be connected to the two terminalsof an external power supply. By means of multiple connection elements,different antennas applied on the substrate as electrically conductivestructures can, for example, be contacted. Due to the small dimensionsand reduction of thermal stresses, connection elements according to theinvention are particularly suited for panes on which multiple connectionelements can be disposed, even with little distance between them. Theconnection elements are preferably disposed in a line. The distancebetween adjacent connection elements is preferably from 5 mm to 50 mm,particularly preferably from 10 mm to 20 mm. This arrangement isadvantageous from a production technology standpoint and for aestheticreasons. In particular, the connection elements in this relativearrangement can be fixed, for example, before soldering in a sharedmounting bracket. The side edges of the soldering regions of thedifferent connection elements are preferably disposed parallel to eachother and can have, relative to the (imaginary) line on which theconnection elements are disposed, any angle, preferably from 5° to 90°,particularly preferably from 10° to 40°. The crimped regions of thedifferent connection elements are preferably disposed on the same sideof the (imaginary) line. Such an arrangement is particularlyspace-saving.

The substrate has a first coefficient of thermal expansion. Theconnection element has a second coefficient of thermal expansion. In anadvantageous embodiment of the invention, the difference between thefirst and the second coefficient of thermal expansion is less than5×10⁻⁶1° C., particularly preferably less than 3×10⁻⁶1° C. Because ofthis, the thermal stresses in the pane are reduced and better adhesionis obtained.

The substrate contains, preferably, glass, particularly preferably flatglass, float glass, quartz glass, borosilicate glass, and/or soda limeglass. However, the substrate can also contain polymers, preferablypolyethylene, polypropylene, polycarbonate, polymethyl methacrylate,polystyrene, polybutadiene, polynitriles, polyester, polyurethane,polyvinyl chloride, polyacrylate, polyamide, polyethylene terephthalate,and/or copolymers or mixtures thereof. The substrate is preferablytransparent. The substrate preferably has a thickness from 0.5 mm to 25mm, particularly preferably from 1 mm to 10 mm, and very particularlypreferably from 1.5 mm to 5 mm.

The first coefficient of thermal expansion is preferably from 8×10⁻⁶/°C. to 9×10⁻⁶/° C. The substrate preferably contains glass that has,preferably, a coefficient of thermal expansion from 8.3×10⁻⁶/° C. to9×10⁻⁶/° C. in a temperature range from 0° C. to 300° C.

The second coefficient of thermal expansion is preferably from 9×10⁻⁶/°C. to 13×10⁻⁶/° C., particularly preferably from 10×10⁻⁶/° C. to11.5×10⁻⁶/° C., very particularly preferably from 10×10⁻⁶/° C. to11×10⁻⁶/° C., and in particular from 10×10⁻⁶/° C. to 10.5×10⁻⁶/° C. in atemperature range from 0° C. to 300° C.

The connection element according to the invention preferably includes achromium-containing steel with a chromium proportion greater than orequal to 10.5 wt.-%. Other alloy components such as molybdenum,manganese, or niobium result in an improved corrosion resistance oraltered mechanical properties, such as tensile strength or coldformability.

The connection element according to the invention preferably includes atleast 66.5 wt.-% to 89.5 wt.-% iron, 10.5 wt.-% to 20 wt.-% chromium, 0wt.-% to 1 wt.-% carbon, 0 wt.-% to 5 wt.-% nickel, 0 wt.-% to 2 wt.-%manganese, 0 wt.-% to 2.5 wt.-% molybdenum, 0 wt.-% to 2 wt.-% niobium,and 0 wt.-% to 1 wt.-% titanium. The connection element can also includeadmixtures of other elements, including vanadium, aluminum, andnitrogen.

The connection element according to the invention particularlypreferably includes at least 73 wt.-% to 89.5 wt.-% iron, 10.5 wt.-% to20 wt.-% chromium, 0 wt.-% to 0.5 wt.-% carbon, 0 wt.-% to 2.5 wt.-%nickel, 0 wt.-% to 1 wt.-% manganese, 0 wt.-% to 1.5 wt.-% molybdenum, 0wt.-% to 1 wt.-% niobium, and 0 wt.-% to 1 wt.-% titanium. Theconnection element can also include admixtures of other elements,including vanadium, aluminum, and nitrogen.

The connection element according to the invention very particularlypreferably includes at least 77 wt.-% to 84 wt.-% iron, 16 wt.-% to 18.5wt.-% chromium, 0 wt.-% to 0.1 wt.-% carbon, 0 wt.-% to 1 wt.-%manganese, 0 wt.-% to 1 wt.-% niobium, 0 wt.-% to 1.5 wt.-% molybdenum,and 0 wt.-% to 1 wt.-% titanium. The connection element can also includeadmixtures of other elements, including vanadium, aluminum, andnitrogen.

Particularly suitable chrome-containing steels are steels of thematerial numbers 1.4016, 1.4113, 1.4509, and 1.4510 in accordance withEN 10 088-2.

The electrically conductive structure according to the invention has,preferably, a layer thickness from 5 μm to 40 μm, particularlypreferably from 5 μm to 20 μm, very particularly preferably, from 8 μmto 15 μm, and, in particular, from 10 μm to 12 μm. The electricallyconductive structure according to the invention contains, preferably,silver, particularly preferably, silver particles and glass frits.

The layer thickness of the solder material is preferably less than orequal to 6.0×10⁻⁴ m, particularly preferably less than 3.0×10⁻⁴ m.

The solder material according to the invention is leadfree. This isparticularly advantageous in view of the environmental impact of thepane with an electrical connection element according to the invention.In the context of the invention, “leadfree solder material” means asolder material that includes, in accordance with EC Directive“2002/95/EC on the Restriction of the Use of Certain HazardousSubstances in Electrical and Electronic Equipment”, a lead proportionless than or equal to 0.1 wt.-%, preferably no lead.

Leadfree solder materials typically have less ductility thanlead-containing solder materials, such that mechanical stresses betweena connection element and a pane can be less well compensated. However,it has been demonstrated that critical mechanical stresses can clearlybe prevented by means of the connection element according to theinvention. The solder material according to the invention contains,preferably, tin and bismuth, indium, zinc, copper, silver, orcompositions thereof. The proportion of tin in the solder compositionaccording to the invention is from 3 wt.-% to 99.5 wt.-%, preferablyfrom 10 wt.-% to 95.5 wt.-%, particularly preferably from 15 wt.-% to 60wt.-%. The proportion of bismuth, indium, zinc, copper, silver, orcompositions thereof in the solder composition according to theinvention is from 0.5 wt.-% to 97 wt.-%, preferably 10 wt.-% to 67wt.-%, whereby the proportion of bismuth, indium, zinc, copper, orsilver can be 0 wt.-%. The solder composition can contain nickel,germanium, aluminum, or phosphorus at a proportion of 0 wt.-% to 5wt.-%. The solder composition according to the invention contains, veryparticularly preferably, Bi40Sn57Ag3, Sn40Bi57Ag3, Bi59Sn40Ag1,Bi57Sn42Ag1, In97Ag3, Sn95.5Ag3.8Cu0,7, Bi67In33, Bi33In50Sn17,Sn77.2In20Ag2.8, Sn95Ag4Cu1, Sn99Cu1, Sn96.5Ag3.5, Sn96.5Ag3Cu0.5,Sn97Ag3, or mixtures thereof.

In an advantageous embodiment, the solder material contains bismuth. Ithas been demonstrated that a bismuth-containing solder material resultsin particularly good adhesion of the connection element according to theinvention to the pane, by means of which damage to the pane can beavoided. The proportion of bismuth in the solder material composition ispreferably from 0.5 wt.-% to 97 wt.-%, particularly preferably 10 wt.-%to 67 wt.-%, and very particularly preferably from 33 wt.-% to 67 wt.-%,in particular from 50 wt.-% to 60 wt.-%. In addition to bismuth, thesolder material preferably contains tin and silver or tin, silver, andcopper. In a particularly preferred embodiment, the solder materialincludes at least 35 wt.-% to 69 wt.-% bismuth, 30 wt.-% to 50 wt.-%tin, 1 wt.-% to 10 wt.-% silver, and 0 wt.-% to 5 wt.-% copper. In avery particularly preferred embodiment, the solder material contains atleast 49 wt.-% to 60 wt.-% bismuth, 39 wt.-% to 42 wt.-% tin, 1 wt.-% to4 wt.-% silver, and 0 wt.-% to 3 wt.-% copper.

In another advantageous embodiment, the solder material contains from 90wt.-% to 99.5 wt.-% tin, preferably from 95 wt.-% to 99 wt.-%,particularly preferably from 93 wt.-% to 98 wt.-%. In addition to tin,the solder material preferably contains from 0.5 wt.-% to 5 wt.-% silverand from 0 wt.-% to 5 wt.-% copper.

The solder material flows out with an outflow width of less than 1 mmfrom the intermediate space between the solder region of the connectionelement and the electrically conductive structure. In a preferredembodiment, the maximum outflow width is less than 0.5 mm and, inparticular, roughly 0 mm. This is particularly advantageous with regardto the reduction of mechanical stresses in the pane, the adhesion of theconnection element, and the reduction in the amount of solder. Themaximum outflow width is defined as the distance between the outer edgesof the solder region and the point of the solder material crossover, atwhich the solder material drops below a layer thickness of 50 μm. Themaximum outflow width is measured on the solidified solder materialafter the soldering process. A desired maximum outflow width is obtainedthrough a suitable selection of solder material volume and verticaldistance between the connection element and the electrically conductivestructure, which can be determined by simple experiments. The verticaldistance between the connection element and the electrically conductivestructure can be predefined by an appropriate process tool, for example,a tool with an integrated spacer. The maximum outflow width can even benegative, i.e., pulled back into the intermediate space formed by thesolder region of the electrical connection element and an electricallyconductive structure. In an advantageous embodiment of the paneaccording to the invention, the maximum outflow width is pulled back ina concave meniscus into the intermediate space formed by the solderregion of the electrical connection element and the electricallyconductive structure. A concave meniscus is created, for example, byincreasing the vertical distance between the spacer and the conductivestructure during the soldering process, while the solder is still fluid.The advantage resides in the reduction of mechanical stresses in thepane, in particular, in the critical region present with a large soldermaterial crossover.

In an advantageous embodiment of the invention, the contact surface ofthe connection element has spacers, preferably at least two spacers,particularly preferably at least three spacers. The spacers are disposedon the contact surface between the connection element and the soldermaterial and are preferably formed in one piece with the connectionelement, for example, by stamping or deep drawing. The spacerspreferably have a width of 0.5×10⁻⁴ m to 10×10⁻⁴ m and a height of0.5×10⁴ m to 5×10⁻⁴ m, particularly preferably of 10⁻⁴ m to 3×10⁻⁴ m. Bymeans of the spacers, a homogeneous, uniformly thick, and uniformlyfused layer of the solder material is obtained. Thus, mechanicalstresses between the connection element and the pane can be reduced andthe adhesion of the connection element can be improved. This isparticularly advantageous with the use of leadfree solder materials thatcan compensate mechanical stresses less well due to their lowerductility compared to lead-containing solder materials.

In an advantageous embodiment of the invention, at least one contactbump, which serves for contacting the connection element with thesoldering tool during the soldering process, is disposed on the surfaceof the solder region of the connection element facing away from thesubstrate. The contact bump is preferably curved convexly at least inthe region of contacting with the soldering tool. The contact bumppreferably has a height of 0.1 mm to 2 mm, particularly preferably of0.2 mm to 1 mm. The length and width of the contact bump is preferablybetween 0.1 and 5 mm, very particularly preferably between 0.4 mm and 3mm. The contact bumps are preferably implemented in one piece with theconnection element, for example, by stamping or deep drawing. For thesoldering, electrodes whose contact side is flat can be used. Theelectrode surface is brought into contact with the contact bump. Forthis, the electrode surface is disposed parallel to the surface of thesubstrate. The contact region between the electrode surface and thecontact bump forms the soldering point. The position of the solderingpoint is determined by the point on the convex surface of the contactbump that has the greatest vertical distance from the surface of thesubstrate. The position of the soldering point is independent of theposition of the solder electrode on the connection element. This isparticularly advantageous with regard to a reproducible, uniform heatdistribution during the soldering process. The heat distribution duringthe soldering process is determined by the position, the size, thearrangement, and the geometry of the contact bump.

The electrical connection element has, preferably at least on thecontact surface facing the solder material, a coating (wetting layer)that contains nickel, copper, zinc, tin, silver, gold, or alloys orlayers thereof, preferably silver. By this means, improved wetting ofthe connection element with the solder material and improved adhesion ofthe connection element are achieved.

The connection element according to the invention is preferably coatedwith nickel, tin, copper, and/or silver. The connection elementaccording to the invention is particularly preferably provided with anadhesion-promoting layer, preferably made of nickel and/or copper, and,additionally, with a solderable layer, preferably made of silver. Theconnection element according to the invention is coated, veryparticularly preferably, with 0.1 μm to 0.3 μm nickel and/or 3 μm to 20μm silver. The connection element can be plated with nickel, tin,copper, and/or silver. Nickel and silver improve the current-carryingcapacity and corrosion stability of the connection element and thewetting with the solder material.

The shape of the electrical connection element can form one or aplurality of solder depots in the intermediate space of the connectionelement and the electrically conductive structure. The solder depots andwetting properties of the solder on the connection element prevent theoutflow of the solder material from the intermediate space. The solderdepots can be rectangular, rounded, or polygonal in design.

The object of the invention is further accomplished through a method forproduction of a pane according to the invention with at least oneelectrical connection element, wherein

a) the connection element is connected to the connection cable bycrimping in a region,b) solder material is applied on the bottom of the solder region,c) the connection element with the solder material is disposed on aregion of an electrically conductive structure that is applied on aregion of a substrate, andd) the connection element is connected, with energy input, to theelectrically conductive structure.

The solder material is preferably applied to the connection element as aplatelet or a flattened drop with a fixed layer thickness, volume,shape, and arrangement. The layer thickness of the solder materialplatelet is preferably less than or equal to 0.6 mm. The shape of thesolder material platelet preferably corresponds to the shape of thecontact surface. If the contact surface is implemented, for example, asa rectangle, the solder material platelet preferably has a rectangularshape.

The introduction of the energy during the electrical connecting of anelectrical connection element and an electrically conductive structureoccurs preferably by means of punches, thermodes, piston soldering,preferably laser soldering, hot air soldering, induction soldering,resistance soldering, and/or with ultrasound.

The electrically conductive structure can be applied to the substrate bymethods known per se, for example, by screen-printing methods. Theapplication of the electrically conductive structure can take placebefore, during, or after the process steps (a) and (b).

The connection element is preferably used in heated panes or in paneswith antennas in buildings, in particular, in automobiles, railroads,aircraft, or watercraft. The connection element serves to connect theconducting structures of the pane to electrical systems that aredisposed outside the pane. The electrical systems are amplifiers,control units, or voltage sources.

The invention further includes the use of the pane according to theinvention in buildings or in means of transportation for travel on land,in the air, or on water, in particular in rail vehicles or motorvehicles, preferably as a windshield, rear window, side window, and/orglass roof, in particular as a heatable pane or as a pane with anantenna function.

The invention is explained in detail with reference to drawings andexemplary embodiments. The drawings are schematic representations andnot true to scale. The drawings in no way restrict the invention. Theydepict:

FIG. 1 a perspective view of a first embodiment of the pane according tothe invention,

FIG. 2 a cross-section A-A′ through the pane of FIG. 1,

FIG. 3 a cross-section A-A′ through an alternative pane according to theinvention,

FIG. 4 a cross-section A-A′ through another alternative pane accordingto the invention,

FIG. 5 a cross-section A-A′ through another alternative pane accordingto the invention,

FIG. 6 a cross-section B-B′ through another alternative pane accordingto the invention,

FIG. 7 a cross-section B-B′ through another alternative pane accordingto the invention,

FIG. 8 a detailed flow chart of the method according to the invention.

FIG. 1 and FIG. 2 depict in each case a detail of a pane according tothe invention in the region of the electrical connection element 3. Thepane comprises a substrate 1, which is a 3-mm-thick thermallyprestressed single pane safety glass made of soda lime glass. Thesubstrate 1 has a width of 150 cm and a height of 80 cm. An electricallyconductive structure 2 in the form of a heating conductor structure isprinted on the substrate 1. The electrically conductive structure 2contains silver particles and glass frits. In the edge region of thepane, the electrically conductive structure 2 is widened to a width of10 mm and forms a contact surface for an electrical connection element3. The connection element 3 serves for the electrical contacting of theelectrically conductive structure 2 with an internal power supply via aconnection cable 5. The connection cable 5 includes an electricallyconductive core that is implemented as a conventional stranded wireconductor made of copper. The connection cable 5 further includes apolymer insulating sheathing (not shown) that is removed in the endregion to the length of 4.5 mm to enable the electrical contacting ofthe electrically conductive core of the connection cable 5 with theconnection element 3. A covering screenprint (not shown) is alsosituated in the edge region of the substrate 1.

The electrical connection element 3 is made of steel of the materialnumber 1.4509 in accordance with EN 10 088-2 (ThyssenKrupp Nirosta®4509) with a coefficient of thermal expansion of 10.5×10⁻⁶1° C. in thetemperature range from 20° C. to 300° C. The material thickness of theconnection element 3 is, for example, 0.4 mm. The connection element hasa region 11 with a length of, for example, 4 mm, which is crimped aroundthe end region of the connection cable 5. For this, the side edges ofthe crimped region 11 are bent around the connection cable 5 andsqueezed therewith. The crimp is disposed such that the region of thesubstrate 1 bent around points away from the substrate 1. By this means,an advantageously small angle can be realized between the crimped region11 and the substrate 1. However, in principle, the reversed arrangementof the crimp is also possible.

The connection element 3 further has a substantially rectangular, flatsolder region 10, which is connected to the crimped region 11 via atransition region 12. The solder region 10 has, for example, a length of4 mm and a width of 2.5 mm. The transition region 12 has, for example, alength of 1 mm. The solder region 10 is disposed on the side of thecrimped region 11 that faces the extension direction of the connectioncable 5. The angle between the solder region 10 and the crimped region11 is, for example, 160°. The transition region 12 is implemented flat,but can, for example, alternatively also be implemented curved and/orbent.

The surface of the solder region 10 facing the substrate 1 forms acontact surface 8 between the electrical connection element 3 and theelectrically conductive structure 2. Solder material 4, which effects adurable electrical and mechanical connection between the electricalconnection element 3 and the electrically conductive structure 2, isapplied in the region of the contact surface 8. The solder material 4contains 57 wt.-% bismuth, 40 wt.-% tin, and 3 wt.-% silver. The soldermaterial 4 has a thickness of 250 μm. The solder region 10 is connectedto the electrically conductive structure 2 via the contact surface 8over its entire area.

FIG. 3 depicts a cross-section through an alternative embodiment of thepane according to the invention with the connection element 3. Thecontact surface 8 of the connection element 3 is provided with asilver-containing wetting layer 6, for example, with a thickness ofroughly 5 μm. This improves the adhesion of the connection element 3. Inanother embodiment, an adhesion-promoting layer, made, for example, ofnickel and/or copper can be situated between the connection element 3and the wetting layer 6.

FIG. 4 depicts a cross-section through an alternative embodiment of thepane according to the invention with the connection element 3. Spacers 7are disposed on the contact surface 8 of the connection element 3. Forexample, four spacers 7, of which two spacers 7 can be discerned in thesection depicted, can be disposed on the contact surface 8. The spacers7 are stamped into the solder region 10 of the connection element 3 andthus implemented in one piece with the connection element 3. The spacers7 are shaped as spherical segments and have a height of 2.5×10⁻⁴ m and awidth of 5×10⁻⁴ m. By means of the spacers 7, the formation of a uniformlayer of the solder material 4 is promoted. This is particularlyadvantageous with regard to the adhesion of the connection element 3.

FIG. 5 depicts a cross-section through an alternative embodiment of thepane according to the invention with the connection element 3. A contactbump 9 is disposed on the surface of the soldering region 10 of theconnection element 3 facing away from the substrate 1 and opposite thecontact surface 8. The contact bump 9 is stamped into the solder region10 of the connection element 3 and thus implemented in one piece withthe connection element 3. The contact bump 9 is shaped as a sphericalsegment and has a height of 2.5×10⁻⁴ m and a width of 5×10⁻⁴ m. Thecontact bump 9 serves for the contacting of the connection element 3with the soldering tool during the soldering process. By means of thecontact bump 9, a reproducible and defined heat distribution is ensuredindependent of the exact positioning of the soldering tool.

FIG. 6 depicts a cross-section through an alternative embodiment of thepane according to the invention with the connection element 3. Theelectrical connection element 3 includes, on the contact surface 8facing the solder material 4, a recess with a depth of 250 μm, which isstamped into the solder region 10 and which forms a solder depot for thesolder material 4. Outflow of the solder material 4 from theintermediate space can be completely prevented. By this means, thethermal stresses in the pane are further reduced.

FIG. 7 depicts a cross-section through an alternative embodiment of thepane according to the invention with the connection element 3. Theconnection element 3 has, in addition to the crimped region 11, thetransition region 12, and the solder region 10, a further region 13,adjacent the solder region 10. The further region 13 and the transitionregion 12 with the crimped region 11 are connected to opposing edges ofthe solder region 10.

FIG. 8 depicts in detail a method according to the invention forproduction of a pane with an electrical connection element 3.

Test specimens were produced with the substrate 1 (thickness 3 mm, width150 cm, and height 80 cm), the electrically conductive structure 2 inthe form of a heating conductor structure, the electrical connectionelement 3 according to FIG. 1, and the solder material 4. The connectionelement 3 was made of steel of the material number 1.4509 in accordancewith EN 10 088-2, which has a coefficient of thermal expansion of10.0×10⁻⁶1° C. in the temperature range from 20° C. to 200° C. and acoefficient of thermal expansion of 10.5×10⁻⁶/° C. in the temperaturerange from 20° C. to 300° C. The substrate 1 was made of soda lime glasswith a coefficient of thermal expansion of 8.30×10⁻⁶/° C. in thetemperature range from 20° C. to 300° C. The solder material 4 containedSn40Bi57Ag3 and had a layer thickness of 250 μm. The connection element3 was soldered onto the electrically conductive structure 2 at atemperature of 200° C. and a processing time of 2 seconds. No criticalmechanical stresses were observed in the pane. The connection of thepane to the electrical connection element 3 via the electricallyconductive structure 2 was durably stable. With all specimens, it waspossible to observe, with a temperature difference from +80° C. to −30°C., that no substrate 1 broke or showed damage. It was possible todemonstrate that, shortly after soldering, the panes with the solderedconnection element 3 were stable against a sudden temperature drop.

In comparative examples with connection elements that had the same shapeand were made of copper or brass, clearly greater mechanical stressesoccurred and with a sudden temperature difference from +80° C. to −30°C., it was observed that the pane had major damage shortly aftersoldering. It was demonstrated that panes according to the inventionwith glass substrates 1 and electrical connection elements 3 accordingto the invention had better stability against sudden temperaturedifferences. This result was unexpected and surprising for the personskilled in the art.

LIST OF REFERENCE CHARACTERS

-   -   (1) substrate    -   (2) electrically conductive structure    -   (3) electrical connection element    -   (4) solder material    -   (5) connection cable    -   (6) wetting layer    -   (7) spacer    -   (8) contact surface of the connection element 3 with the        electrically conductive structure 2    -   (9) contact bump    -   (10) solder region of the connection element 3    -   (11) crimped region of the connection element 3    -   (12) transition region between the crimped region 11 and the        solder region 10    -   (13) another region of the connection element 3

A-A′ section line

1. A pane with at least one electrical connection element, comprising atleast: a substrate, on a region of the substrate, an electricallyconductive structure, on a region of the electrically conductivestructure, a connection element that comprises at least achromium-containing steel, wherein the connection element has a regioncrimped around a connection cable and a solder region and wherein thesolder region is connected to the electrically conductive structure viaa leadfree solder material.
 2. The pane according to claim 1, whereinthe angle between the solder region and the crimped region is from 120°to 180°, preferably from 150° to 170°.
 3. The pane according to claim 1,which includes two to six connection elements, which are preferablydisposed in a line, with the distance between adjacent connectionelements preferably from 5 mm to 50 mm, particularly preferably from 10mm to 20 mm.
 4. The pane according to claim 1, wherein the materialthickness of the connection element is from 0.1 mm to 2 mm, preferablyfrom 0.2 mm to 1 mm, particularly preferably from 0.3 mm to 0.5 mm. 5.The pane according to claim 1, wherein the difference between thecoefficient of thermal expansion of the substrate and the coefficient ofthermal expansion of the connection element is less than 5×10⁻⁶/° C. 6.The pane according to claim 1, wherein the connection element comprisesat least 66.5 wt.-% to 89.5 wt.-% iron, 10.5 wt.-% to 20 wt.-% chromium,0 wt.-% to 1 wt.-% carbon, 0 wt.-% to 5 wt.-% nickel, 0 wt.-% to 2 wt.-%manganese, 0 wt.-% to 2.5 wt.-% molybdenum, 0 wt.-% to 2 wt.-% niobium,and 0 wt.-% to 1 wt.-% titanium.
 7. The pane according to claim 6,wherein the connection element comprises at least 77 wt.-% to 84 wt.-%iron, 16 wt.-% to 18.5 wt.-% chromium, 0 wt.-% to 0.1 wt.-% carbon, 0wt.-% to 1 wt.-% manganese, 0 wt.-% to 1 wt.-% niobium, 0 wt.-% to 1.5wt.-% molybdenum, and 0 wt.-% to 1 wt.-% titanium.
 8. The pane accordingto claim 1, wherein the substrate contains glass, preferably flat glass,float glass, quartz glass, borosilicate glass, and/or soda lime glass.9. The pane according to claim 1, wherein the electrically conductivestructure contains at least silver, preferably silver particles andglass frits and has a layer thickness of 5 μm to 40 μm.
 10. The paneaccording to claim 1, wherein the layer thickness of the solder materialis less than or equal to 6.0×10⁻⁴ m.
 11. The pane according to claim 1,wherein the solder material contains tin and bismuth, indium, zinc,copper, silver, or compositions thereof.
 12. The pane according to claim11, wherein the solder material contains 35 wt.-% to 69 wt.-% bismuth,30 wt.-% to 50 wt.-% tin, 1 wt.-% to 10 wt.-% silver, and 0 wt.-% to 5wt.-% copper, or wherein the solder material contains 90 wt.-% to 99.5wt.-% tin, 0.5 wt.-% to 5 wt.-% silver, and 0 wt.-% to 5 wt.-% copper.13. The pane according to claim 1, wherein the connection element has atleast a wetting layer that contains nickel, tin, copper, and/or silver.14. A method for production of the pane with at least one electricalconnection element according to claim 1, comprising: connecting theconnection element to the connection cable by crimping in a region,applying the solder material on the bottom of the solder region,disposing the connection element with the solder material on a region ofan electrically conductive structure that is applied on a region of asubstrate, and connecting the connection element, with energy input, tothe electrically conductive structure.
 15. A method comprising: applyingthe pane with at least one electrical connection element according toclaim 1, in buildings or in means of transportation for travel on land,in the air, or on water, in particular in rail vehicles or motorvehicles, preferably as a windshield, rear window, side window, and/orglass roof, in particular as a heatable pane or as a pane with anantenna function.